Makeshift draught-excluder? (7)

I believe the answer is:

stopgap

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'makeshift' is the definition.
(I know that makeshift can be written as stopgap)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for stopgap that I've seen before include "Improvisation" , "A temporary substitute or solution" , "caretaker" , "Provisional" , "Interim" .)

I've seen this clue in The Globe and Mail.

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